Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, so the read-only nature is covered. The description adds meaningful behavioral context beyond the annotations: the tool returns a JSON result, is robust to partial image modification ('높은 확률로 워터마크를 확인'), supports common formats, and carries a per-call cost of 10 points — a practical operational detail agents benefit from. No contradiction with annotations exists.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is tight and purpose-front-loaded: one clear directive sentence followed by three high-value specifications (JSON return, robustness, format support) and a cost note. Every sentence earns its place. Minor redundancy exists from stating the same idea in both English and Korean, but the whole remains compact and scannable.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a low-complexity, single-parameter read tool with readOnlyHint=true and full schema coverage, the description is nearly complete: it covers return format (JSON), supported formats, robustness characteristics, and cost. With no output schema present, it would benefit from a brief note on the JSON response structure, but that gap is minor for a tool returning a watermark code.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the single image_url parameter is already fully documented (downloadable https URL, allowed MIME types, 50MB cap). The description's mention of PNG/JPEG support is consistent with but less specific than the schema, adding minimal new meaning. Baseline 3 is appropriate when the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb+resource pair: 'Read the invisible watermark code embedded in an image.' It clearly states the tool's function (read/query, return as JSON) and is naturally distinguished from closely related siblings like set_watermark (write operation), draw_watermark_image, and draw_watermark_pdf (visible watermark drawing). The bilingual phrasing reinforces rather than obscures the purpose.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage context is implied rather than explicit: the read-vs-set/draw contrast with sibling names signals when to pick this tool, and the description adds practical conditions (works on partially modified images, supports PNG/JPEG, costs 10 points per call). However, there is no explicit 'when to use' statement, no named alternative, and no exclusion guidance such as 'use draw/set_watermark to embed watermarks instead.'

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.